大黄鱼(Larimichthys crocea)补体C3和C4基因的分子特征及表达分析

MOLECULAR CHARACTERIZATION AND EXPRESSION OF COMPLEMENT COMPONENT C3 AND C4 IN LARGE YELLOW CROAKER LARIMICHTHYS CROCEA

本文测定了大黄鱼C3(L.c-C3)和C4(L.c-C4)基因的c DNA全序列。结果表明,L.c-C3和L.cC4序列全长分别为4962bp和5088bp,分别编码1653和1695个氨基酸,N端信号肽序列分别为23和19个氨基酸。推导的氨基酸序列结构分析表明大黄鱼C3和C4与已报道的补体C3、C4同样都具有在功能上比较重要的残基以及保守的硫酯区。分子进化分析表明,L.c-C3和L.c-C4分别与鮸鱼C3、C4的氨基酸同源性最高。实时荧光定量PCR结果显示,L.c-C3和L.c-C4在健康大黄鱼的肝脏、脾脏、肠、鳃、心脏、脑、肌肉和胃这8种组织中都有表达,其中肝脏的表达量最高。在大黄鱼胚胎不同发育时期(从2细胞期到初生仔鱼)中,L.c-C3在各个阶段没有明显的变化,而L.c-C4的表达量有明显升高。溶藻弧菌(Vibrio alginolyticus)侵染的大黄鱼肝脏和脾脏中,L.c-C3和L.c-C4的m RNA表达量均明显上调。该结果表明,大黄鱼肝组织C3和C4基因表达变化与溶藻弧菌的侵染密切相关,揭示了C3和C4在大黄鱼抗细菌免疫反应中具有重要的作用。

We reported the primary sequence of Larimichthys crocea complement component C3(L.c-C3) and C4(L.c-C4) c DNA. The L.c-C3 open reading frame(ORF) is 4962 bp encoding 1653 amino acids(aa) with a putative signal peptide of 23 amino acid residues. L.c-C4 open reading frame(ORF) is 5088 bp encoding 1695 aa with a putative signal peptide of 19 amino acid residues. The deduced amino acid sequence shows that the L.c-C3 and L.c-C4 has conserved residues and domains known to be critical for C3 and C4 functions. Phylogenetic analyses of L.c-C3 and L.c-C4 showed that L. crocea was most closely related to Miichthys miiuy. The m RNA expressions of L.c-C3 and L.c-C4 were detectable at different tissues. L.c-C3 and L.c-C4 were expressed in a wide range of adult tissues, with the highest expression levels in the liver. During the different development stages from fertilized egg to newborn larvae of the large yellow croaker the highest expression levels of L.c-C3 gene was not found, but L.c-C4 was significantly up-regulated. Bacterial challenge experiments showed that the levels of L.c-C3 and L.c-C4 m RNAs expression were up-regulated in the liver and spleen of adult large yellow croaker. The results show that L.c-C3 and L.c-C4 m RNAs expression in the large yellow croaker were influenced by bacterial stress. The L.c-C3 and L.c-C4 m RNAs expressions in the large yellow croaker were influenced by bacterial stress and they may play an important role in immunity mechanisms. This study will deepen our understanding on the functions of L.c-C3 and L.c-C4 m RNAs and the molecular mechanism of innate immunity in teleosts.